This invention pertains to an apparatus for facilitating the discharge of lading through an oulet in a vessel. By the term vessel is meant to include industrial bins, hoppers, railway hopper cars, transportation containers, ships, or other structures containing particulate lading to be discharged therefrom through an opening therein.
A frequent problem which has received the attention of prior practitioners in this art is the "bridging" which occurs at the discharge outlet of a vessel. The particulate material builds up across the outlet to create a blockage which prevents the further discharge of material.
Various approaches have been used to prevent bridging. One such approach is to shape the outlet portion of the vessel in a manner which will facilitate flow of the particulate solids. Another solution involves the vibration of the vessel which induces enough agitation to deter stoppage of the outlet flow. Still another approach is the provision of a vibrating or oscillating member at the outlet as shown by U.S. Pat. No. 767,591 which issued on Aug. 16, 1904, to William E. Nickerson. A wide variety of vibrators and oscillators are now available for attachment to the outlet and/or the vessel.
In Holm U.S. Pat. No. 3,637,115 sound vibrations are utilized to facilitate sliding of particulate material down a hopper.
In Cymbalisty U.S. Pat. No. 3,407,927 a member or obstruction is provided adjacent the outlet of the vessel containing the particulate material. This member is vibrated at a frequency in the range of 5000-12000 cycles per minute along the central axis of the outlet. Simultaneously, it is vibrated at a lower frequency in directions transverse to the outlet. This latter frequency is preferably in the range of 400 to 1000 cycles per minute. The transverse vibrations, since they are of a lesser frequency, do not appreciably densify the mass of particulate matter, but they do continuously compact and release the mass against the walls of the outlet to facilitate discharge of the material.
However, none of these techniques have been effective in preventing bridging during lading discharge. In fact, bridging is such a serious problem that some lading simply cannot be unloaded from vessels because of the bridging problem. Example of such lading are asbestos and wood flour.
Furthermore, vibrators and oscillators apply considerable stresses to the hopper, particularly fatigue, and failures due to continuous vibration during unloading are not uncommon.
In Matson U.S. Pat. No. 3,788,527 there is provided a quick release aerator that stores a large volume of air under significant pressure and then releases the air into the storage vessel, producing a blast which dislodges stuck or bridged lading.
In the Matson arrangement an accumulator for storing compressed air has mounted within it a valve used to release the air and direct it into the vessel through an air discharge conduit.
While this arrangement is effective is dislodging lading in the general path of the air discharge conduit, it is not effective to dislodge lading which is not in the path of the discharge conduit.
Thus in order to dislodge all the lading in a hopper or vessel in accordance with the Matson arrangement, it is necessary to mount a plurality of aerators in such a manner that the air discharge conduits extend generally into all parts of the vessel. Thus a large number of aerators are required per vessel to dislodge and unload the lading.